memchr.c

来自「Many C samples. It is a good sample for 」· C语言 代码 · 共 44 行

/*  File   : memchr.c
    Author : Richard A. O'Keefe.
    Updated: 25 May 1984
    Defines: memchr()

    memchr(src, chr, len)
    searches the memory area pointed to by src extending for len bytes,
    looking for an occurrence of the byte value chr.  It returns NullS
    if there is no such occurrence.  Otherwise it returns a pointer to
    the FIRST such occurrence.

    See the "Character Comparison" section in the READ-ME file.
*/

#include "strings.h"

#if	VaxAsm

char *memchr(src, chr, len)
    char *src;
    char chr;
    int len;
    {
	asm("locc 8(ap),12(ap),*4(ap)");
	asm("bneq L1");
	asm("movl r1,r0");
	asm("L1: ret");
    }

#else  ~VaxAsm

char *memchr(src, chr, len)
    register char *src;
    register int chr;		/* should be char */
    register int len;
    {
	while (--len >= 0)
	    if (*src++ == chr) return src-1;
	return NullS;
    }

#endif	VaxAsm